1. Field of the Invention
The present invention relates to device for measuring aerosol concentrations in a chamber or machine.
2. Description of the Related Art
Monitoring of aerosol concentrations, especially lubricant mist in the drive spaces of internal combustion engines or in the housings of power trains, for example, in printing presses, is of major importance in avoiding damage, since a rapid rise in the oil mist concentration suggests rupture of the lubricating film. Because of the heat of friction that then develops, oil vapor is formed, which recondenses to oil mist in the drive space and thus leads to a rapid rise in oil mist concentration. An incipient hazard can be recognized from this and further damage avoided by appropriate measures, for example, stopping of the machine.
In addition to the already described oil mist formation, so-called blow-by can occur in piston engines between the piston and cylinder wall as a result of damaged piston rings, owing to lubricating film tears in the bearings, which, if not recognized in time, lead to seizing of the pistons. An increase in oil mist density with a simultaneous temperature rise as a result of the hot combustion gases reaching the crankshaft housing suggest blow-by.
Devices to indicate oil mist concentrations in the drive spaces of internal combustion engines are known (EP-B-0 071 391), in which the oil mist is withdrawn by suction from the drive space and passed through a chamber that contains a device to measure absorbance. The significant design and operating expense (e.g., pumps, maintenance), the possible de-mixing of the aerosol "oil mist" on the way to and through the chamber, and the time delay during measurement are drawbacks.
A device of the type mentioned at the outset is known from DD-A-239 474 or GB-A-2 166 232, in which a measurement probe is provided for each drive of an internal combustion engine, in which each measurement probe is directly arranged in the interior of the corresponding drive space and connected via an optical or electrical transmission path to a central evaluation unit situated outside of the internal combustion engine.